The present invention relates to a lubricant composition for improving fatigue life, more particularly, to a lubricant composition capable of extending the fatigue life of machine parts such as gears and bearings and imparting corrosion resistance thereto by virtue of specific additives admixed with a lubricant base material.
As is known, the lubricant used for the lubrication of gears, bearings and the like should have high anti-scoring performance because these machine parts must withstand a very high pressure when they are in operation. Recent investigations of these machine parts after actual use, however, have revealed that the phenomenon of scoring takes place very rarely and most of troubles in these machine parts are ascribable to the damages by fatigue such as pitting and the like.
In view of the above circumstances, various types of lubricant compositions for extending fatigue life of machine parts have been developed and proposed in the prior art technology of lubrication. For example, Takao Katayama and Masahiko Takesue, fellow employees of the inventors of the present application have developed a lubricant composition for improving fatigue life by formulating a specific sulfur compound to a lubricant base material as is disclosed in Japanese Patent Kokai No. 59-11397 (U.S. Ser. No. 500,264) now Pat. No. 4,501,678. The performance of this improved lubricant composition is, however, not quite satisfactory and it is eagerly desired to develop a further improved lubricant composition in respect of not only extension of the fatigue life but also corrosion resistance of the machine parts lubricated therewith.